Reactivating metallic contaminated catalyst employed in cracking hydrocarbons



Feb. 4, 1964 G. A. MILLS ETAL 3,120,484 REACTI-VATING METALLICCONTAMINATED CATALYST EMPLOYED IN CRACKING HYDROCARBONS Original FiledJune l5, 1954 Hg. z.

A K WMZ ATTORNEY United States Patent O REAcrrvATING MnratucCONTAMINATED cATALYsr EMPLOYED 1N caAcrnNG nvnnocARoNs George AlexanderMills, Swarthmore, Thomas H. Milli- 1 Claim. (Cl. 20S- 120) Thisinvention relates to the cracking of hydrocarbons and particularly tothe cracking of hydrocarbons over solid catalysts contaminated by heavymetals of the group consisting of vanadium and nickel. This applicationis a division of Serial No. 436,814, filed June l5, 1954.

As explained in an article by G. A. Mills, Industrial and EngineeringChemistry, vol. 42, page 182 (1950), deposited contaminants of the groupcomprising vanadium and nickel on a catalytic cracking catalyst,contribute to the loss of catalyst activity or selectivity. Hydrocarbonsin the presence of materials such as vanadium, nickel, vanadium oxide,and nickel oxide at elevated temperatures, such as encountered in acracking Zone, tend to form carbonaceous deposits. Hence such materialscan be designated as coking catalysts. This coke forming tendency ofheavy metal oxides is related in part to the dehydrogenation activity ofthe heavy metal oxides. The carbonaceous deposits result in part fromthe polymerization of the unsaturates resulting from the dehydrogenationof hydrocarbons by the catalytic influence of vanadium oxide and nickeloxide.

Throughout the industrial history of catalytic cracking, much attentionhas been given to the problems connected with the effect of heavy metalsand heavy metal oxides on the products distribution and other aspects ofthe catalytic cracking operations. Some deposited contaminants, such asstrontium and barium are so rarely encountered that they can be ignored.Some metals such as iron are encountered much more frequently thancontaminants such as strontium. The troubles attributable to a givenconcentration of a contaminant such as iron are of a smaller order ofmagnitude than those arising from the same concentration of contaminantsofthe group consisting of vanadium and nickel materials. Catalysts areconveniently considered merely on the basis of their content of vanadiumand nickel contaminants without regard to the amount of iron or otherdeposited contaminants. Copper oxide, although only rarely encounteredin crudes, and then usually in combination with vanadium, is sometimesdeposited on catalysts from equipment. Copper oxide adversely increasesthe incremental coke factor even more than the same Weight of ferricoxide, but requires no separate consideration because of the infrequencyof copper diiculty except in combination With vanadium and/ or nickelcontaminants.

Partly because'heavy metal contaminants have accumulated on catalysts,it has generally been the practice to replace a catalyst after use for aperiod of months in a fixed bed operation. In those catalytic crackinginstallations having a Zone of -moving particles of catalyst (eg.gravitating beads or fluidized catalyst), it has been customary toreplace constantly a small fraction of the total amount of catalyst incirculation. Accordingly, the useful life of the catalyst in a systemhaving a zone of moving particles has been discussed in terms of thecatalyst replacement rate. It has been known that the catalystreplacement rates Were significantly smaller during the processing of agas oil distillate containing only small amount (for example, `0.1 partper million) of Ser. No. 436,814. 29, 1959, Ser. No.

3,120,484 Patented Feb. 4, 1964 heavy metals than in the processing ofgas oils containing relatively large (for example, about 1 or 2 p.p.m.)of heavy metals. lt has been known that solid catalyst particles weresusceptible to abnormal aging involving high rates of catalystreplacement as a result of excessively large amounts of heavy metals inthe hydrocarbons subjected to cracking. Some petroleum distillates (i.e.gas oils) boiling above the range of gasoline have had no ash content,and others have had up to about 50 p.p.m. heavy metals.

Even during the processing of gas oils containing very small amounts ofheavy metals, it has been possible for the catalyst to becomecontaminated with heavy metals by reason of impurities introducedthrough the process equipment and/or by accident. It has been necessaryto replace the thus contaminated catalyst because of its abnormal agingeven though the heavy metal content of the catalyst Was not attributableto the stock being processed.

Although catalyst particles containing excessive amounts of contaminantsof the group consisting of vanadium and nickel have not been suitablefor use in the cracking zone, it has been feasible to tolerate smallamounts of such contaminants. The catalyst Withdrawn from a circulatingcatalyst installation has sometimes contained a significant amount ofvanadium and nickel, such as about 20 p.p.m. Heretofore it has generallybeen considered not commercially feasible to employ as a crackingcatalyst a solid containing more than about 200 p.p.m. of depositedcontaminants of the group consisting of vanadium and nickel.

The vanadium and nickel content of catalyst particles comprisingactivated (Le. not deactivated) contaminants leaving the de-coking kilnor oxidation zone (or entering the cracking zone) is in the form ofvanadium oxide and nickel oxide. Chemical analyses are based on theamounts of vanadium oxide and nickel oxide found in the particles. rTheconcentrations of contaminants in parts per million also refer tovanadium oxide and nickel oxide. During the passage of vanadium oxideand/or nickel oxide through a hydrocarbon cracking Zone, it isconceivable that a part thereof may be reduced to the metallic state.The presence of metallic vanadium and/ or nickel may contribute to theadverse result of a high incremental coke factor. Regardless of theextent, if any, of such metal formation, Within the cracking zone,catalyst particles entering the cracking zone with vanadium oxide and/ornickel oxide contaminants possess a high incremental coke factor whichis a consistent and reliable standard of comparison in evaluatingcatalysts.

In the cracking zone, a significant portion of the heavy metal contentof a hydrocarbon charge tends to be deposited on the solid catalyst.Accordingly, the effect of the heavy metals in the charge stock iscumulative as it affects the catalyst.

If a stock containing a relatively large amount, -for example 2 p.p.m.,of heavy metals, is cracked -by conventional procedures, the catalystcan be employed for only a relatively few cycles before accumulating aheavy metals contaminant deposition greater than about 200 p.p.m.

A residuum stock has been considered generally unsuitable for catalyticcracking, by reason of the large amount of heavy metals in this type ofhydrocarbon stock. A crude having an ash of 500 p.p.m. yields a 10%bottoms containing about 5000 p.p.m. metals. Even a crude containing 0.1p.p.m. ash yields a 10% bottoms of 1 p.p.m. metals. Although petroleumfractions containing large amounts (e.g. 2 p.p.m. of heavy metals) havebeen thermally cracked, commercial cracking of high metals stock overconventional catalysts by conventional procedures has not beenindustrially practical. In the the active catalytic surface of thecatalyst particles is quite application of George Alexander Mills,Thomas H. unaffected by the hydrocarbon gas under these deactiva-Milliken, J r., and Donald H. Stevenson, Serial No. 421,226, tionconditions. led April 6, 1954, for Cracking of Heavy Hydro- Althoughvarious deactivating agents and/or techniques carbons, and assigned tothe same assignee as herein, or combinations of techniques `fordeactivating vanadium the present invention are useful as a supplementt0 the the present invention, which concerns the cracking of hymethod ofcracking heavy hydrocarbons described in said lo drocarbons in thepresence of cracking catalysts comaPPllCatl0nprising deactivated heavymetal contaminants of the In accordance with the present invention, ahydrocargroup consisting of vanadium and nickel.

hOn Charge Steek. Whether 0f the gas Oll 0r IeSdnnnl The data relatingto catalytic cracking is bcstunderstood type. but having at least SeineComponents boiling above in connection with the results of a Cat A tesi.The the range 0f light geSOhne. 1S heated t0 an elevated tem- 15standard ltest for the usefulness of a cracking catalyst, perature andthereafter introduced into a circulating sometimes designated as theCat-A test, described in an stream (eg. gravitating bed or uidized zone)0f Solid article by Alexander, Proceedings American Petroleum particlesof cracking catalyst. It should be especially Institute (HI), 27, page57 (1947), is utilized in several noted that the particles of crackingcatalyst contain more of the examples. It should be noted that the gasgravity than 400 but less than 40 000 parts per million of de- 20 (whichis desirably above l 00) is one of the useful guides positedcontaminants of the group consisting of vanadium in detecting theadverse effects of deposited contaminants and nickel said contaminantsbeing deactivated to pro- Still more useful however, are data on thecoke factors vide an incremental coke factor less than one-half the andincremental coke factors as derived from the Cat. A incremental cokefactor attributable to the particles tests The coke factoi is the ratioof coke produced under characterized by the corresponding quantities ofthe corretest conditions to the coke produced under standard conspondingoxides of vanadium and nickel. The hydrocarditions so controlled as toachieve the same yield of gasoybon is subjected to cracking conditionsincluding a temline.

perature Iwithin the range from about 700 to about ll00 As explained inan article, entitled Factors Controlling F. during the conversion overthe catalyst comprising the Aging of Cracking catalysts, by G. A. Millsand H. A. deactivated heavy metal contaminants. A vapor stream Shabaker,Petroleum Refiner, 30, page 97, graphs (eg.

products therein are subjected to fiactional distillation, senting thedata relating to the standard of comparison in thereby obtaining afraction constituting a high octane calculating coke factors from theexperimental data gasoline. A gas stream gas oil, and bottoms ormixtures Because a coke factor of 100 represents what was arerecirculated to the cracking zone. is one less than the coke factor (eg.coke factors of l, 3 The vanadium and/or nickel contaminants aredeactiand 2 correspond to incremental coke factors of 0, 2 and vated bymeans of a deactivating agent which may be in- 1 respectively). Thus theincremental coke factor protroduced during catalyst manufacture, duringthe passage vides a useful criteria concerning the adverse coke-formofthe particles through the cracking zone, and/or during ing tendencies ofa catalyst under the standard testing a special processing stepsubsequently to the decoking of conditions. An incremental coke factorof 2.00, for exthe catalyst particles and prior to the return of thecataample, indicates adverse coking at least four times as lystparticles to the cracking zone. The deactivating agent severe as auincremental coke factor of 0.5.

may combine with the vanadium and/or nickel contami- Using ges OllSentirely free from heeVy metals, and nants in a chemical orquasi-chemical manner, or the defresh nneorltanlnated catalysts, theYield 0f geSOlne een activation may be of a more strictly physicalnature be regulated by controlling the cracking conditions The Acarbonaceous deposit can be formed substantially amount 0f Coke fOrIIled1S dependent UPOn the Severity only upon heavy metal contaminants bypreliminary treat- 0f Cracking COnClItIOnS 21nd/ 0r gasoline Yleld lfOnly ment with a normally gaseous hydrocarbon under dehy. 20% gasolineis obtained, the coke is about 0.7% of the drogenation conditions,whereby aparticular kind of active feed, but lf 40% gasoline results,approximately 3.7.0 0f carbon forms at the sites of the vanadium and/ornickel the feed fOrmS Coke even Under Optlrnnrn COnClltlPnS- thedeactivating agent is introduced in a deactivating zone dltlOnS: The.Coke factor is a term Well established in between the decoking zone andhydrocarbon conversion eatalytle Cracking teehnOlOgY t0 eXPreSS theratlO 0f the zone, coke formed to the coke which would have been formedCertain features characterize that embodiment of the nnder Sneh OptnnunlConflltlons ntythe Same Yleld 0f gest?- present invention in which thevanadium and nickel conline Under mild eraeklng Condltlons resulting 1n20/5 from the group consisting of methane, ethane, ethylene, t10n Was40%- propane, propylene, butane, butylene, butadiene, and ln theaeeenlpenylng draWlngS FIGURE l 1S a Sellemixtures thereof, andconveniently designated as a hydromatie rePreSentntlOIl Of a lOW Sheet0f the method 0f carbon gas having a molecular weight less than 60 or asthe present invention. O ne group of the several groups a normallygaseous hydrocarbon, is passed over the de- 70 of embodiments of theinvention is schematically repvanadium oxide and nickel oxide areeffective in bringing cross section, said apparatus being suitable forconductabout some deposition of active carbon at the location ing anembodiment of the method of FIGURE 2. of the metal deposits. However,the major portion of Reference is made to several examples whichillustrate prior art practices, controls, and embodiments of theinvention.

Example I A clay catalyst was impregnated to contain about 450 p.p.m. ofnickel as nickel oxide. This catalyst was tested with a standard gas oilunder standard cracking conditions. The relatively unsatisfactoryperformance of this catalyst was attributable almost entirely to thepresence of the deposited nickel contaminant.

This contaminated catalyst was subjected to a stream of methane at agaseous hourly space rate of 30 v./v. hour. The catalyst particles andgas were both preheated to maintain a temperature of 1100 F. in thedeactivating chamber. There was thus produced on the catalyst particles0.06% active carbon, which active carbon was deposited only on thoseportions Where nickel oxide was present. The nickel was deactivated bythe coating of active carbon to provide `an incremental coke `factorabout four-tenths that of the contaminated catalyst. 'In the standardcracking tests the following results were noted:

It should be noted that the presence of the active carbon on thecatalyst particles made -it possible to produce a larger amount ofgasoline and a significantly smaller amount of coke.

Example 1I The nickel contaminated catalyst par-ticles of the previousexample were treated with butane gas at 1100 F. at an hourly space rateof 30 v./v. hour to for-m an active carbon deposit on the nickelcontaminated portions of the catalyst particles. On analysis, theparticles were found to contain 0.2% active carbon.

The catalyst particles after deactivation With butane were employed inthe standard cracking test and found to have an incremental coke factorwith the following results Deacti- Initial Contamivated by Clay natedwith Carbon Nickel from utane j Gasoline, percent 28. 4 18.2 21. 5 Gas,percent 3. 4 3. 8 3. 8 Coke, percent 1. 7 3. 9 2. 9 Gas Gravity 1.190.44 0.71 Coke Factor 1.20 4.80 1. 75 Incremental Coke F 0.20 3. 30 0.75 Percentage Decrease 77. 4

Thus the deactivation of the nickel oxide by butane further increasedthe production of gasoline and signicantly decreased the amount of cokeformed, as compared to the amount formed without butane deactivation.

inasmuch as the reaction of low molecular Weight (ie. less than 60)hydrocarbons and oxides of metals such as vanadium and nickel is veryrapid, it is appropriate to utilize the gas lift as the deactivationchamber when ernploying said low molecular weight hydrocarbons (alsodesignated as normally gaseous hydrocarbons) as the deactivating agent.Although an average-sized catalyst bead may travel from the bottom tothe top of a gas lift in a very short time, the metallic oxide depositson the catalyst can he coated with a sufiicient lm of carbon at theseelevated temperatures even during the brief passage of each particlethrough the gas lift.

The type of carbon deposited on the catalyst particles by the reactionof the low molecular Weight hydrocarbon with the metallic oxide may bedifferent from that which results from the deposition of `carbonaceousmaterial during the cracking of liquid hydrocarbons. Such differentproperties are most easily described by the term activate carbon todistinguish the carbon 0f the -deactivated particles from thecarbonaceous deposits or coke resulting from ordinary catalytic crackingoperations. The solid deposit from the reaction of a hydrocarbon gas ofless than 60 -molecular weight may have a smaller particle size, smallerhydrogen content, less volatilizable matter, and larger iadsorptivesurface than the carbonaceous material deposited during conventionalcracking.

The diiferences in the location of the carbon-containing deposits on thecatalyst particles is even more important than 'the differences in thecomposition of the deposits. At temperatures employed in the activatecarbon deposition, the silica-alumina `catalyst is substantially insertas regards normally gaseous hydrocarbons. Although the oxides ofvanadium "and nickel exert their catalytic iniluence on the normallygaseous hydrocarbon, thereby depositing the active carbon only at thesites of the heavy metal contaminant, the cracking catalyst exerts nocracking influence on the normallyv gaseous hydrocarbons at theconditions employed for such deactivation. Accordingly the carbondeposition `at the metal contaminant sites does not interfere with tnecrack-ing activity of the catalyst.

What is claimed is:

ln a method for continuously cracking metal contaminated hydrocarbonswhich :are liquid above 400 F. in which silica-alumina cracking catalystgranules lare circulated through a hydrocarbon cracking Zone and througha regeneration Zone and are lcontinuously recirculated through the`cracking and regeneration zones with incremental amounts of freshsilica-alumina cracking catalyst granules Vadded. at a rate maintainingthe average catalytic eifeetiveness atan acceptable level, and `in whichthe silicaalumina cracking catalyst granules contain an averageconcentration of more than 400 but less than 40,000 ppm. of heavy metalcontaminants of the group consisting of vanadium and nickel, saiddeposited heavy metal contaminants having been deposited from previoushydrocarbon charge containing compounds of vanadium and nickel ascontaminants, the improvement which consists essentially of; directingregenerated silica-alumina cracking catalyst `granules having anave-rage concentration of more than 400 but less than 40,000 p.p.rn. ofheavy metal contaminants of the ygroup consisting of vanadium and nickelinto a deactivating zone maintained at a temperature of about 1100 F.;depositing carbon selectively lon to the contaminants iby subjecting thecatalyst `granules at 1100" F. to 'a stream of butane; and `directingthe granules characterized by carbon selectively deposited on vanadiumand nickel contaminants into the cracking zone, whereby the amount ofcarbonaceous deposit formed in the none for cracking the hydrocarbonswhich are liquid above 400 F. is so small that the inctemental `cokefactor is less than 1/2 the incremental coke factor of granulescharacterized by corresponding quantities iof a catalytically activeform of the oxides of vanadium and nickel, and whereby the catalystreplacement rate is significantly less than in the absence of saidbutane treatment of the regenerated catalyst.

References Cited in the tile of this patent UNITED STATES PATENTS UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 120, 484February '-4, George Alexander Mills et al.,

, It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read asCorrected below.

Column 6, line 20, for "insert" read inert u,

signed and sealed this imh'dayff July 1964;

(SEAL) Attest:

EsToN G. JOHNSON EDWARD J. BRENNER Attestng Officer Commissioner ofPatentsl

